Freezer conveyor

ABSTRACT

A conveyor freezer employing a self-supporting conveyor arranged in a helical stack for carrying discrete food items into the freezer, through the helical stack for a predetermined period of time, and out of the freezer. A major portion of the weight of the helical belt stack is supported by a rotatable turntable A portion of the lowermost tier of the stack is elevated and supported by a ramp structure which preferably comprises a pair of runners engaging lower surfaces of outwardly extending flange portion of side links of the belt. The belt is preferably driven by a single drive unit at a location outside of the freezer enclosure, remote from the stack, by a single pair of sprockets. A timing sprocket is preferably employed to control belt pitch along the infeed section of the belt.

BACKGROUND OF THE INVENTION

The invention relates generally to conveyors and, more particularly, toa conveyor capable of transporting food product through a freezer in ahelical path.

The use of helical or spiral conveyors for carrying food product throughfreezers enables acceptable dwell time to be maintained in conjunctionwith acceptable product throughput rates, with efficient use of space.U.S. Pat. No. 3,315,492 discloses a freezer employing such a helicalconveyor, wherein the tiers of the conveyor are supported by horizontalarms which extend into the stack. It has been recognized thatcompactness of freezers of this type may be improved by increasing thenumber of tiers without increasing the vertical dimension of thefreezer, by making the belt self-supporting, which enables thehorizontal arms to be eliminated, thereby permitting closer spacing ofadjacent tiers while maintaining desired clearance for product. U.S.Pat. No. 3,938,651 discloses a conveyor arrangement wherein the belt isarranged in a self-supporting stack and the stack is supported on asecond conveyor which is driven to rotate the stack. However, provisionof a satisfactory conveyor for supporting the stack has proven to beproblematic, and it has been found that a helical belt stackmanufactured in accordance with the teachings of this patent aresusceptible to collapsing under certain conditions.

U.S. Pat. No. 4,565,282 states as one of its objects to eliminate thedisadvantages of prior art installations such as that of U.S. Pat. No.3,938,651, which have not been able to carry the pile or stack through acontinuous complete revolution due to the ingoing or outgoing lower partof the conveyor belt. The installation of U.S. Pat. No. 4,565,282comprises two endless chains which are arranged under the belt pile soas to carry the belt through a complete revolution. However, thearrangement of U.S. Pat. No. 4,565,282 is complicated and expensive andis believed to be susceptible to problems due to ice formationinterfering with proper functioning of rolling elements in theapparatus. U.S. Pat. No. 4,899,871 discloses an arrangement which isintended to address the problem of ice formation obstructing ballmovement by employing a chain comprising overlapping links which areintended to exclude ice from the path of rolling elements. This proposedarrangement further increases the number of moving parts and adds to theexpense and complexity of the apparatus.

SUMMARY OF THE INVENTION

In accordance with the invention, there is provided a novel and improvedconveyor system of the type employing a self-supporting helical beltstack.

In accordance with one aspect of the invention, a major portion of theweight of the helical belt stack is supported by a rotatable turntable.The turntable is preferably substantially rigid and orientedhorizontally. In the preferred embodiment, the belt enters the helicalstack at the upper end thereof and exits the helical stack at the lowerend thereof. In other embodiments, the belt may proceed in the reversedirection.

In accordance with a further aspect of the invention, the helical beltstack is located within an enclosure and is driven by a drive unit whichengages the belt outside of the freezer enclosure, and does not drivethe turntable directly. One or more timing sprockets may be employed tomaintain desired belt pitch at one or more locations along the path ofthe conveyor belt. In accordance with an additional aspect of thepreferred embodiment of the invention, a portion of the lowermost tierof the stack is elevated and supported by ramp means which provideclearance for belt discharged from the stack therebeneath, then isguided in a downwardly sloping path to the turntable. The ramp meanspreferably comprise a pair of runners which engage lower surfaces ofoutwardly extending flange portions of the side links of the belt.

The turntable preferably comprises a substantially rigid structurehaving inner and outer circular rails for supporting respective innerand outer sides of the belt arranged in the helical belt stack.

Further aspects of the invention may be appreciated from the followingdescription and claims, and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic partially exploded perspective view of afreezer in accordance with a preferred embodiment of the invention;

FIG. 2 is a diagrammatic plan view of the conveyor of the freezer ofFIG. 1;

FIG. 3 is a perspective view showing a portion of the conveyor indetail, with portions broken away and portions shown in section forillustrative purposes;

FIG. 4 is a diagrammatic sectional elevational taken substantially alongline 4--4 of FIG. 2;

FIG. 5 is a diagrammatic plan view of the turntable of the conveyor;

FIG. 6 is a sectional view taken substantially along line 6--6 of FIG.5;

FIG. 7 is a diagrammatic sectional view taken substantially along line7--7 of FIG. 1;

FIG. 8 is a diagrammatic elevational view taken substantially along line8--8 in FIG. 2;

FIG. 9 is a fragmentary elevational view illustrating a timing sprocketin the conveyor;

FIG. 10 is a fragmentary plan view corresponding to FIG. 9;

FIG. 11 is a diagrammatic view taken substantially along line 11--11 inFIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention is preferably embodied in a conveyor freezer 10 foreffecting rapid heat transfer from a plurality of discrete food items 12to a fluid such as air which is maintained at sub-ambient temperatureswithin an enclosure 14. The preferred enclosure has first and secondaccess openings 16 and 18 therein. A conveyor 20 extends through theaccess openings 16 and 18 to transport the food items through theenclosure. The illustrated freezer employs a mechanical refrigerationapparatus 22 to cool the air in the freezer. Other embodiments of theinvention might employ cryogenic refrigeration apparatus, e.g., meansfor injecting liquid nitrogen (N₂) and/or liquid carbon dioxide (CO₂),instead of, or in conjunction with, such mechanical refrigerationapparatus.

The illustrated enclosure comprises four vertical sidewalls 24, a topwall 26 and a bottom wall or floor 28. The walls are preferablythermally insulated to facilitate maintenance of large temperaturedifferentials between the interior and exterior of the enclosure. Atleast one door 30 is preferably provided to enable access to theinterior of the enclosure for cleaning and maintenance.

The conveyor generally comprises a first portion defining a generallyhelical stack 32, and a second portion, indicated generally at 34, whichfollows a predetermined path between the uppermost tier and thelowermost tier of the stack, externally of the stack. Referring to FIG.2, the stack 32 in the illustrated embodiment rotates in a clockwisedirection. It should be appreciated, however, that in other embodiments,the stack might rotate in the opposite direction.

In the illustrated embodiment, the second portion 34 of the beltincludes an infeed section 40 leading from an on-loading station 50outside of the enclosure 14 to the uppermost tier 36 of the stack; asubstantially linear output section 42 leading from the lowermost tier44 of the stack to an off-loading station 46 outside of the enclosure;and a return portion 48 which extends from the off-loading station 46 tothe on-loading station generally beneath the aforedescribed portions ofthe belt, and partially beneath the stack 32.

For convenience of description, the helical stack 32 will be describedherein as a series of tiers, each tier comprising a single 360° portionof the helical stack and having upper and lower ends. It should beunderstood that the upper and lower ends of the tiers do not connoteinterruptions in the continuity of the belt. To the contrary, the beltas described herein is endless and continuous.

The uppermost tier 36 of the stack has an upper end 38a contiguous withthe substantially linear infeed section, and a lower end 38b contiguouswith the upper end of the second tier. The lowermost tier has a lowerend 52 adjoining the output section, and an upper end 54 disposedsubstantially thereabove, 360° upstream therefrom in the helical stack.In the embodiment illustrated in FIG. 1, six tiers are shown. However,in most commercial operations, it is believed that a greater number oftiers are likely to be employed. The number of tiers in the helicalstack will vary among particular embodiments according to the needs ofthe particular freezer application. A plurality of intermediate tiers 56are disposed between the uppermost and lowermost tiers. The uppermosttier 36 and each of the intermediate tiers 56 is supported by contactwith the respective tier immediately therebeneath.

The belt is composed of inner side links 58 and outer side links 60defining opposite flexible sidewalls, and a plurality of generallyhorizontal, transverse connecting rods 62 extending between the oppositesides. A wire or plastic overlay 64 supported on the rods 62 provides asupport surface for food product.

The inner and outer side links 58 and 60 are arranged in alternating,overlapping fashion along each side of the belt. Each of the outer sidelinks is of generally L-shaped configuration, comprising an upstanding,generally vertical portion 66 and a flange portion 68 which extendsgenerally horizontally outward from the bottom of the upstanding portion66, then extends upward to form a generally vertical tab. Each of theinner links 58 is also of generally L-shaped configuration, comprisingan upstanding portion 72 and a generally horizontal flange 74 whichextends inwardly relative to the belt along the lower portion of theupstanding portion.

Each of the links 58 and 60 has a pair of openings 76, 78 near thebottom of its respective upstanding portion. In each link, one of theopenings 76 is substantially circular, having a diameter slightlygreater than the diameter of its associated belt rod. The adjacentopening is a horizontal slot 78 which permits the belt rod 62 to sliderelative to the link with a sufficient degree of relative movement toenable the belt to turn from a substantially straight configuration tothe curved configuration assumed in the helical stack 32. Each of therods 62 has enlarged heads 63 at each end. Each of the enlarged heads 63is disposed between the upstanding portion 66 and the tab 70 of arespective one of the outer side links. This constrains the outer sidelinks from moving inward or outward relative to the rods beyond alimited range of motion defined by the distance between the innersurface of the tab 70 and the outer surface of the upstanding portion 66of the outer side link.

In accordance with an aspect of the invention, a major portion of theweight of the helical stack and food product supported thereon iscarried by a rotatable turntable 80. The preferred turntable is arelatively rigid structure as contrasted with prior art conveyors andthe like which have used multiple rolling elements and other movingparts supporting a rotating helical belt stack. The preferred turntable80 is a substantially rigid, horizontally oriented wheel comprisinginner and outer circular rails 82 and 84 which are radially spaced fromone another by a distance approximately equal to the distance betweenthe opposite sides of the belt.

In the illustrated embodiment, a major portion (i.e., greater thanone-half) of the lowermost tier of the stack 32 is engaged by andsupported by the turntable 80, with the inner rail 82 of the turntabledirectly supporting the inner side of the belt and the outer rail 84supporting the outer side of the belt. A vertical lip 86 extends upwardabout the inner periphery of the inner rail 82 to define a minimum innerradius for the lowermost tier 44 of belt and constrain the lower tieragainst horizontal displacement relative to the turntable.

The inner and outer rails 82 and 84 are connected to a central hub 94 bysix radially extending spokes 87. Roller assemblies 88 are positioned onthe undersides of the respective spokes at their points of intersectionwith the inner rail 82, with the rollers having horizontal axes orientedradially relative to the turntable 80.

The rollers 88 travel on a circular track 90 on a base 92 positionedcoaxially beneath the turntable 80. The base 92 comprises a plurality ofvertical legs 93 supporting the circular track 90, with radial braces 95connecting the legs to a central post 96. The post interfits with thehub 94 to maintain the turntable rotatably centered on the base. Thepreferred track 90 has a groove or channel 98 formed therein to supportthe rollers 88 and maintain the rollers in their proper location on thetract, with a wear strip 99 spanning the bottom of the channel orgroove.

The rollers 88 on the turntable are preferably made of an acetylplastic. The track 90 comprises a steel rail having a polymeric wearstrip thereon.

One of the problems inherent in the use of self-stacking belts is thatremoval of belt from the bottom of the stack or, conversely, infeed ofbelt into the bottom of the stack, requires that a portion of the beltadjacent the upper end of the lowermost tier be supported in a manner toprovide sufficient clearance for belt to travel therebeneath. Inaccordance with an aspect of the invention, the requisite clearance ispreferably provided by support of a minor portion i.e., less thanone-half, of the first tier of the belt adjacent the upper end of thefirst tier through the use of a ramp means comprising inner and outerrunners 100 and 102. In the illustrated embodiment, in which belt isremoved from the stack at the lower end, the runners 100 and 102 areconfigured to lift the belt as it enters the lowermost tier. As the beltproceeds along the first tier, the belt is maintained at sufficientelevation to provide clearance for belt exiting the stack immediatelybeneath the upper portion of the lowermost tier, then slopes downward tothe turntable 80. In the illustrated embodiment, the runners 100 and 102extend through an arc of between about 45° and 120°, preferably about80°, along the sides of the helical stack to support the belt in thismanner.

In accordance with a further aspect of the invention, the runners 100and 102 engage the undersides of the flange portions 68 of the outerlinks on the opposite sides of the belt to provide support for thesubject portion of the lowermost tier 44 and the tiers thereabove. Thisenables the lowermost tier to be lifted without requiring a transversesupport to extend entirely beneath and across the width of the belt, andwithout interference with the belt beneath the portion of belt that isbeing lifted.

The inner runner 100 has a first portion 108 which slopes slightlyupward in order to lift the belt as described above, and a secondportion 110 which slopes gradually downward to lower the belt onto theturntable. The outer runner is similarly configured. The runners 100 and102 are supported on part-cylindrical inner and outer vertical walls 104and 106 which are disposed respectively along the inside and outside ofthe helical stack 32 through an arc approximately coextensive with therunners 100 and 102.

The illustrated runners 100 and 102 engage the belt in sliding contact.The runners are preferably made of an ultra high molecular weight (UHMW)polyethylene or other suitable wear resistant polymer. Use of thismaterial provides a relatively low friction sliding engagement with thestainless steel belt, and enables operation to be maintained with nosignificant wear to the belt links due to the sliding contact, and withrelatively little wear to the runners themselves. The illustratedrunners are of substantially rectangular cross section, and are affixedto their respective walls by transverse, generally horizontal screws orother fasteners.

In the preferred embodiment, the belt is driven by a pair of sprocketshaving teeth which extend between the flanges 68 of adjacent outer linkmembers on each side of the belt. The drive sprockets are connected by ahorizontal shaft which is rotated by a conventional chain drive 112 toan electric motor 114 or other suitable drive units. The belt preferablyreverses directions at the drive sprockets.

Turning to the travel of the belt discharged from the lower end of thestack to the output section 42, as the belt leaves the bottom of thestack, it is lifted slightly from the turntable and guided by a pair ofsubstantially linear rails which engage the underside of the outwardlyextending flanges 68 of the outer links 60 on opposite sides of thebelt. The belt proceeds generally horizontally and to clear theturntable and the helical stack 32, then turns upward around a pair ofguide wheels 116 to slope upward toward the off-loading station 46. Theguide wheels 116 engage the upper surfaces of the flanges 68 of theouter links.

The belt proceeds out of the enclosure 14 through an access opening,then at the off-loading station 46, turns downward about a roller 130 toreverse directions and proceeds in an inverted orientation downward backthrough the enclosure, parallel to and beneath the section of the belt,output around a generally cylindrical roller, and from there generallyhorizontally beneath the turntable to a similar cylindrical roller atwhich the belt then turns upward. The inverted belt then turns aboutanother cylindrical roller slope downwardly, parallel to and beneath theinfeed section 40 through an access opening, to the drive sprockets. Thebelt then reverses direction 180° at the drive sprockets and slopesupwardly along a first portion of the infeed section. Then slightlydownward to the top of the helical stack.

The belt overlay comprises a grid or mesh for supporting food product.As best seen in FIG. 3, the overlay comprises a series of elongatedloops which enables belt pitch, i.e., distance between connecting rods,to vary without buckling of the overlay. Due to the configuration of theoverlay, certain soft food products are susceptible to damage when thebelt pitch changes, particularly at the infeed portion of the belt, whenthe food product has not been frozen and, therefore, has a soft,vulnerable surface in contact with the overlay. Excessive changes inbelt pitch can cause soft food products, such as hamburger patties andfish fillets, to be distorted or torn, leaving the products with adistorted shape, a visible crack, or other flaw after being frozen.Moreover, portions of the product may be pinched and torn away from thefood product, which not only damages the food product, but alsoincreases the difficulty of cleaning the belt between uses. Generally,decrease in belt pitch, i.e., compression or collapsing of the belt, isbelieved to be more deleterious to food than increase in belt pitch,i.e., expansion of the belt. In accordance with a further feature of theinvention, to control the belt pitch along the infeed section, a pair oftiming sprockets 118 engage the infeed portion of the belt and thereturning portion of the belt directly therebeneath, at approximatelythe location at which the orientation of the infeed section of the beltchanges from an upwardly sloping orientation to a slightly downwardsloping orientation. The timing sprocket 118 is configured substantiallysimilarly to the drive sprockets described above. As shown in FIGS. 9and 10, the sprocket 118 engages the belt with teeth 128 which protrudebetween the flanges 68 of adjacent outer links 60 on the opposite sidesof the belt. The timing sprockets 118 on either side are affixed to acommon axle or shaft 120. This timing arrangement aids in maintainingsubstantially uniform spacing between the links along both sides of thebelt, which is important to proper stacking of the belt in the helix,and is also important to proper driving of the belt. The timingsprockets are believed to aid in avoiding skipping or jumping of linksover the drive sprockets, and also contribute to avoidance of pitchingof product on the infeed section of the belt by maintainingsubstantially uniform belt pitch along the upwardly sloping portion ofthe infeed section.

If it is desired to avoid any decrease in belt pitch after product hasbeen placed on the belt, the timing sprockets 118 may be employed tomaintain a tightly compressed or collapsed configuration of the beltfrom the infeed section to the upper end of the uppermost tier of theconveyor. If necessary, one or more additional timing sprockets may beemployed to assist in maintaining the desired pitch. As shown in FIG. 8,the inner edge of the belt in the stack is fully collapsed, i.e., theouter links 60 along the inner edge of the belt have their edgesabutting one another. Thus, if the belt is entirely collapsed orcompressed across its entire width in the infeed section, then when thebelt enters the helical stack, the outer edge of the belt is expandedwhile the inner edge remains collapsed or compressed.

In the illustrated embodiment of the invention, as shown in FIG. 1, thebelt is maintained in the infeed section in a slightly collapsed orcompressed mode, such that as it enters the helix, the inner edgecollapses or compresses, while the outer edge expands. Employment ofthis geometry provides for relatively little change in belt pitch at anyparticular point across the width of the belt. It will be appreciatedthat the belt in the embodiment of FIG. 1 is driven along both edges, ascontrasted with certain "expand only" belt configurations wherein thebelt is driven, i.e., subjected to tension, along only an inner edgethereof.

The portions of the belt which are substantially planar, e.g., theupwardly sloping portion of the infeed and output sections 40 and 42,may be supported by appropriately sloped surfaces fixed beneath thebelt, or by other suitable means. To guide the downwardly slopingportion of the infeed section onto the turntable, guide rails 126 aredisposed on opposite sides of the belt, engaging the outwardly extendingflanges 68 of the outer links. To form the upper tier of the helicalstack at the proper radius, guides or wear strips 122 are affixed to thewalls on either side of the belt, and engage the outer surfaces of theouter links on opposite sides of the upper tier near the upper endthereof. The guides 122 are substantially coextensive with the walls 104and 106, extending through an arc of about 80°.

From the foregoing, it will be appreciated that the invention provides anovel and improved conveying system for freezers or for otherapplications. The invention is not limited to embodiment described aboveor to any particular embodiment.

While the terms "horizontal," "vertical," etc. have been used herein torefer to the belt in a particular orientation corresponding to thebottom of the belt being disposed generally horizontal and the sidesvertical, it will be appreciated that during normal use, variousportions of the belt assume various different orientations, and that theinvention herein is not limited to use of the belt in particularorientation or orientations.

The invention is believed to provide advantages over known prior artsystems employing self-stacking belts in that the system of theinvention may be constructed in embodiments which employ relatively fewmoving parts, and a relatively simple structure which facilitatescleaning and maintenance of components inside the freezer enclosure. Theconveyor is driven entirely by a single external drive unit, without theneed for motors or other drive components to be disposed within thefreezer enclosure. The turntable rotates freely rather than beingdirectly driven, and the rotation of the turntable is the effect ofapplication of force to the belt by the drive unit externally of thefreezer enclosure.

The illustrated freezer operates with relatively little slack in thesystem as compared with known commercially available conveyor freezerunits, many of which include four to five feet of slack belt. Theillustrated system also differs from some known commercial systems inthat it drives the belt along both edges by engaging the side links withthe drive sprockets.

The invention is believed to provide a practical and economicalalternative to more expensive, more complex systems which are moredifficult to clean and maintain in commercial use. Further aspects ofthe invention are pointed out in the following claims.

What is claimed is:
 1. A freezer comprising:a structure defining an enclosed interior; means for maintaining said enclosed interior below ambient temperature; a continuous belt following an endless path at least partially disposed within said enclosed interior for carrying food product; said belt comprising a first portion defining a generally helical stack which includes (a) a lowermost tier having an upper end and a lower end, (b) a series of intermediate tiers, and (c) an uppermost tier; each of said intermediate tiers and said uppermost tier being supported at least partially by the tier immediately therebeneath; said belt further comprising a second portion following a predetermined path between the upper tier and the lower tier externally of said helical stack; a substantially rigid rotatable turntable for supporting a major portion of said lower tier in a substantially horizontal configuration; means for guiding said second portion of said belt in said predetermined path externally of said helical stack; means for driving said belt; and ramp means for lifting and supporting a minor portion of said lowermost tier above said turntable in a configuration such that, proceeding from the upper end of the lowermost tier to the lower end thereof, the lowermost tier first slopes slightly upward to facilitate transition of belt between the lower end of the stack and the second portion of the belt, then slopes downward to the turntable.
 2. A freezer in accordance with claim 1 wherein said ramp means comprises a pair of runners disposed on opposite sides of said lower tier.
 3. A freezer in accordance with claim 1 wherein said ramp means supports a portion of said lowermost tier through an arc of between about 45° and about 120°.
 4. A freezer in accordance with claim 1 wherein said second portion comprises an off-loading section extending outward from the lower tier of said helical stack to a delivery location, an infeed section extending from an onloading location to the uppermost tier of said stack, and a return portion extending from said off-loading section to said onloading section;said means for driving said belt comprising a pair of drive sprockets engaging opposite sides of the belt; said return portion having a section extending beneath and substantially parallel to said infeed section and adjoining said infeed section at said pair of sprockets such that said belt reverses direction as it engages said drive sprockets; a pair of timing sprockets spaced from said drive sprockets and engaging, in timed relation, both said infeed portion of said belt and said section of said return portion of said belt extending beneath and substantially parallel to said infeed section. 